How can the error "supplied argument is not a valid MySQL result resource" be resolved in PHP when using mysql_num_rows()?

The error "supplied argument is not a valid MySQL result resource" typically occurs when the result set returned by a MySQL query is not valid, which can happen due to a failed query or connection issue. To resolve this error, you should first check if the query was successful and the result set is valid before using functions like `mysql_num_rows()`. 

// Check if the query was successful and the result set is valid
$result = mysql_query($query);
if (!$result) {
    die('Invalid query: ' . mysql_error());
}

// Now you can safely use mysql_num_rows() on the valid result set
$num_rows = mysql_num_rows($result);

Keywords

PHP mysql_num_rows() MySQL error resource

Related Questions